A scattershield is a steel bellhousing designed to protect you in the event of a clutch/flywheel breakage. Its a bit more expensive and its larger. If you car about safety or plan on racing a lot, i'd get one. Like said above, the mcleod/FMS bell is a good one. I run it. It comes with all new bolts.
An aluminum flywheel has a few benefits. It will allow you to rev up faster (its about 12lbs lighter than a stocker I believe) and its less wear and tear on your rotating assembly and main bearings. I run an aluminum flywheel. If your gonna be buying a new one, i'd buy an aluminum one. If you ever build a stroker down the road, you can use it on the stroker. It comes with a 28 and 50 oz weight and a little bolt incase you run 0 balance. Only bad thing about it is its pricey.
You will not need a driveshaft spacer, thats for 94/95's with a tremec. A new trans mount is a good idea. I run prothane trans and motor mounts fyi. You will need an extended fork if you run a scattershield to keep the cable alignment perfect. You will need to grind the welds on your xmember and slide it back. Unless things changed for the newer tremecs, you will need to pick up 3 quarts of gm syncromesh fluid.
I would pick up some arp flywheel bolts. I run the higher strength ones, part # arp-200-2802